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Discussion Starter #1
Hi all, I'm having problems with my turbo 400 not shifting correctly. When I put the trans in drive and accelerate, it stays in first gear up to about 25 mph. Even when I accelerate slowly. It seems like the kickdown switch is activated, but I don't have any kickdown hooked up. I'm not that familiar with 400's, I've only worked on 350's. Any idea's as to what could be causing this? Vacuum modulator, stuck switch on the trans or something. Any help would be appreciated.:thumbup:
 

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Does it shift at all?
If there is no shift at any speed the governor could be stuck or the driven gear stripped.
Or.
It could be either a vacuum or electrical switch concern.
Check for good vacuum at the modulator.
If that is ok then apply 12 volts to the connector at the transmission and listen for a click. If it clicks you have other problems.
No click.
Drop the pan.
Undo the connector, remove the two small bolts.
Remove the cover from the switch and clean it out.
It should click when 12 volts are applied.
 

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Discussion Starter #3
Yeah Stu, it shifts at about 2500 - 3000 RPM's when I'm not getting on it. If I put my foot into it it shifts much higher then that. I checked the modulator and the diaphragm is good. The only connector I see is for what I thought was the reverse lights, and it's disconnected. I don't have any electrical wires connected to the trans.


After I checked the vacuum modulator, I noticed that it had an adjusting screw in the middle of the vacuum port, so I backed it out a couple of turns (4) and I noticed that the shifting seemed to occur a little sooner, but still not where you would consider correct.
 

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Measure the vacuum. Just sticking your finger over the end isn't good enough.
The switch could be open which would raise the shift points.
Try applying 12 volts to it and listen for a click.
It should click on and off as you apply and release the voltage.
Don't screw with the adjuster at the modulator.
400's are usually set very good.
 

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Discussion Starter #5
Thanks for the reply Stu. I checked the vacuum modulator by removing it and placing a vacuum on it. I observed the internal plunger depress and hold. I figured that the internal diaphram is good. I'll check the switch tonight and let you know if I hear a click when I apply 12 volts.
 

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Discussion Starter #8
Well Stu, I checked the kick down switch by applying 12v and it clicked like I guess it's supposed to.

As for Vacuum, I have the line running straight from the intake with no "T" connectors or anything, so the trans is getting straight manifold vacuum. I don't have a gauge handy to check the exact vacuum amount though. Since it is getting straight max vacuum from the engine the only option I could see would be to get a modulator that operated on a lower vacuum?:confused:
 

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Does it have vacuum at the valve?
There aren't any modulators that will run on much lower vacuum.
You could have governor problems.
 

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Discussion Starter #10
Yeah, I have vacuum at the valve. Governor problems..... Well we do have Arnold as Governor now....ha!:D

Sorry, I won't do that again.:(

Anyhow, how would I be able to check for governor problems?
 

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There is a square cover with 4 bolts.
Remove the bolts and pull the governor out.
Check the gear for wear.
Hold the governor by the gear and let weights fall.
Pinch the weights and watch the small valve inside move.
 

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Discussion Starter #12
I know it's been a while since I replied to this post, but I finally had the chance to pull the governor and check the springs. Rather then lean on my knowledge of how loose or tight the springs should be, and how much wear there is on the gear. I just sprang the $20.00 and replaced governor with a new one. The bad news is the transmission still does the same thing. When I start out it up shifts fine from 1-2, and 2-3, but when its in it's final gear (3rd), if I put my foot in it a little, it down shifts back into second.

Don't know where to go from here. Any more suggestions?:confused:
 

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When you put your foot in it a bit you are decreasing vacuum to the valve. This will quite often cause a down shift.
Please measure the vacuum at the valve.
I want you to come back with a number.
At idle and off idle.
I don't know how to state it any easier.
 
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